This invention relates to motorcycles and more particularly to means for mounting an engine on a motorcycle frame.
The vibration caused by internal combustion engines results in discomfort and fatigue for motorcycle operators and passengers. In addition, engine shaking forces are the primary cause of many noise and component fatigue problems. For this reason, a primary concern in the design of motorcycles is the isolation of such engine shaking forces.
Prior art systems for isolating motorcycle engine vibrations have several inherent disadvantages. For example, the engine movement allowed by one type of prior art isolation system causes design problems when considering belt or chain performance. This is often overcome by rigidly attaching the rear swing arm pivot of the motorcycle to the engine. However, this expedient produces another problem relating to handling and road-tire interaction. More particularly, if the swing arm is pivoted on the engine, part of the road load is transmitted through the tire to the swing arm, through the engine, and to the engine mounts so that the road load path is no longer transmitted solely through the frame. As a result, the engine is no longer supported solely by the engine mounting system. In other words, the engine is partially supported by the path consisting of the engine swing arm, the rear shocks and the frame. This requires that an engine mounted in this manner be tuned to adequately address handling problems while attempting to maintain the intended engine isolation. These are often two conflicting goals and often require a compromise which introduces one or more engine mount resonances in the operating range of the vehicle.